In a typical reciprocating internal combustion engine useful work is performed by combustion-generated expanding gases acting on a piston inside a cylinder, which, by causing movement of the engine's solid parts, imparts rotational motion to the engine's crankshaft. In multi-cylinder internal combustion engines a crankshaft's rotational motion is generated by discrete periodic power stroke pulses from individual cylinders. Superimposed on the crankshaft's rotation is an oscillatory or back-and-forth motion associated with periodic cylinder firings during a power stroke pulse of each cylinder, as such, the crankshaft's rotation is typically not absolutely smooth. Such oscillatory motion, i.e. torsional vibration, may be detrimental not only to a perceived smoothness of an engine, but, by possibly disturbing valve event timing, may also negatively affect an engine's performance. Various design dampers have been used to quell such vibrations.
Pendulum dampers that incorporate small masses of varying size to absorb and release vibrational energy antiphase with crankshaft vibration and impulse are known in the industry. The basic principle behind such designs is that as crankshaft rotational speed increases, energy is absorbed by a pendulum mass, but as the rotational speed decreases energy is released back into the crankshaft. Typical of such solutions is the use of heavy-metal inserts associated with a damping medium floating in smooth bores incorporated into crankshaft counterweights. In such a case the heavy-metal inserts surrounded by the damping medium achieve a damping effect in response to vibration energy transmitted by the crankshaft (See U.S. Pat. No. 6,026,776). One drawback of such solutions is the need for special fabrication and assembly of the subject crankshaft.
The present invention provides a torsional vibration damper that does not require internal damping medium and is suited for simple connection to a shaft which requires no special fabrication or assembly.